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[RFI] New equipment shake down...

To: "RFI Mail list at contesting.com" <rfi@contesting.com>
Subject: [RFI] New equipment shake down...
From: "Dave (NK7Z)" <dave@nk7z.net>
Date: Thu, 24 Nov 2022 11:22:27 -0800
List-post: <mailto:rfi@contesting.com>
Howdy,

I am testing a totally new setup for DFing... An untuned, small, shielded loop, and a Icom IC-705.

I want a fast setup and tear down process, and I want to be able to distinguish between multiple RFI sources. The 705 has a waterfall display, so I can see different RFI signals. This allows me to null just the one I am interested in. It is odd to see one pattern null while the other pattern does not null... But it works like a champ!

I have two strong sources close to me, one is a current pain in the rear, (I am getting ready to report it), the other was a pain in the rear, and has been dealt with, (thank you Steve at the ARRL), and is no longer a problem. This pair sources makes a perfect test bed for this sort of thing... So using the above setup I headed out in the field...

I was able to easily distinguish each source of RFI from the other, using the spectrum analyzer style display of the 705. This enabled me to null the RFI source I wanted. Then using the nulls I found via the loop, I was able to take a few bearings, and add them into SigTrax. See attached image.

I have three more images, each closer to the source than the ones attached. Each image show greater and greater detail, as to the location of the RFI source.

I am completely satisfied with the loop, and the directionality of the nulls, even though it was just hand held and loose... Next step is to get the loop mounted in a way I can just yank out of the back of the car, take a bearing, and move on...

I will build a small cross like you see in church, then pivot the horizontal section so it is parallel to the vertical section for storage, and perpendicular to the vertical section for usage.

I'll add some sort of loop hangers, so the loop can be hung in a hurry, (in a repeatable fashion), then permanently mount the feedline and ferrites, (must keep the pattern symmetrical for best nulls), on the vertical part of the mounting frame for the loop.

That will give me a loop, I can coil up and put in a small bag, and a stick...

I can take the stick out, open up the cross piece, hang the loop on it, connect it to the feedline, plug it into the 705, and start DFing...

This should allow for a very fast stop, take a heading, and move on, sort of approach to DFing...

Happy Thanksgiving to all of you!!!

--
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
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